1. Field of the Invention
The present invention relates to a femoral head surface replacement system of hip joint for preservation of a blood vessel, and more particularly, to a surface replacement system for preservation of a blood vessel of a femoral head having a plurality of stems to be assembled which enables bone on-growth and prevents fracture of a femoral neck due to weakness or necrosis caused as blood vessels going to the femoral head are destroyed by a distal metal end in a conventional femoral head surface replacement system.
2. Description of the Related Art
In general, when a coxal articulation connecting a thigh region and a gluteal region requires an artificial joint replacement treatment due to osseous arthritis or femoral head necrosis, a thigh stem can be used therefore. A surface replacement system characteristically preserves blood vessels going to the bone head and stress to the calcar femorale so that one's own bone can be maintained as much as possible.
The hip joint is a classical ball-and-socket joint created by the articulation of the head of the femur with the concave socket of the acetabulum. The body weight is transferred to the lower extremity. The hip joint has a wide range of motion. If the hip joint is destroyed by osteoarthritis and avascular necrosis, it can cause severe pain and limited motion. In order to reduce hip pain and to increase functionality, total hip arthroplasty maybe necessary for some individuals who are suffering from arthritis. A conventional total hip arthroplasty is composed of a small metal ball 22-28 mm to replace the femoral head and neck; and a metal stem that attaches to the femoral shaft.
Unlike a total hip arthroplasty, a surface replacement leaves more of patient's bone in place and does not remove the femoral head and neck as in the case of total hip arthroplasty. A surface replacement system characteristically preserves the patient's own femoral head and neck so that patients can take advantage of a wide range of motion in the hip joint and reduced dislocation compared with conventional total hip arthroplasty. The concept of surface arthroplasty for the treatment of advanced arthritis of the hip in young and active patients has many attractive features because of its improved ability to preserve femoral bone compared to total hip arthroplasty.
FIG. 5 is a view illustrating a state in which a conventional femoral head surface replacement system is used. According to FIG. 5, the conventional femoral head surface replacement system includes a femoral head surface cup 1 having a cavity inside and a distal round marginal end 11 that is open in a lower end thereof, and a stem 2 fixed in inner center of the femoral head surface cup 1 and extending to a lower portion.
The actual femoral head is anatomically not a spherical shape at the peripheral margin, but is anatomically long in anterior and short in posterior. The blood supply of the femoral head is characteristic in adults. Rich subsynoival anastomoses occur at the margins of the articular cartilage. Among these vessels, the subcapsular vessels include postero-superior retinacular vessels, which provide the major blood supply to the femoral heads. These vessels enter the head through multiple small subcapsular sulcus which are located on the posterior-superior neck of the femur. Approximately, seventy percent of the blood supply of femoral heads depends on the retinacular vessels.
Conventional femoral head surface replacement is composed of a mono-block of a distal round margin and stem. Use of this conventional surface replacement system may cause damage to the main supplying blood vessel by the outer margin of the metal cup or by cementation during the operation. The main complications of conventional surface replacement systems are fractures of the femoral neck and advanced collapse of the femoral head. All of these complications are caused by not preserving the vessels of the femoral head. Also, complications are caused by using bone cement on the femoral head. Using bone cement produces fatal pulmonary embolisms intermittently. Heat generated during the hardening time of bone cement, can cause protein necrosis of the femoral head.
Insertion of the fixed length stem through the femoral head into the femoral neck in a conventional head replacement system is also difficult to operate and requires a surgeon's skill. The regular length of fixed femoral stem cannot be adjusted to each patient's state, which can vary due to personal, sexual (male or female), height and racial differences. Thus, this conventional femoral head replacing system is inconvenient to surgeons.